1. Field of the Invention
The present invention relates to a heating apparatus for a passenger vehicle.
2. Description of Related Art
In a passenger vehicle a recirculating system of an operating fluid, such as an oil is provided. Connected to the pressure fluid recirculating system are an oil pump as well as actuators such as fluid cylinders for operating various devices for the vehicle, such as a power steering device. A rotating movement of a crankshaft of an internal combustion engine of the vehicle is transmitted to the oil pump, so that the oil as the operating fluid is discharged from the oil pump and is fed to the operating cylinder as an actuator. As a result, a designated function of the actuator is obtained. In this type of system, the operation of the oil causes heat to be generated, thereby increasing the temperature of the operating fluid (oil) discharged from the oil pump.
In view of the above, an oil cooler is connected to the pressure fluid recirculating system, so that the operating fluid is cooled to prevent the temperature of the oil from exceeding a predetermined value. This means that the heat of the operating fluid is wasted. In other words, in the prior art, the heat generated by the operating fluid was not effectively used.
In view of the above, Japanese Unexamined Patent Publication (Kokai) No. 59-102611 proposes a heating device for an industrial vehicle, where heat as generated by the operating fluid is utilized for heating a cabin of the vehicle. Namely, in the heating device of this patent, a heat exchanger is arranged in a passageway for the operating fluid between an actuator (operating cylinder) and an oil pump, while the heat exchanger is located in a cabin so that the heat exchanger contacts air to be recirculated in the cabin. Thus, at the heat exchanger, heat exchange occurs between the operating fluid and the air recirculated in the cabin, thereby heating the cabin.
In the prior art heating device, the heat exchanger is arranged in the fluid pressure operating system at a location between the actuator and the inlet side of the oil pump. As a result, the operating oil discharged from the oil pump is first fed to the actuator and then to the heat exchanger. In other words, the supply of the operating oil to the heat exchanger occurs after the operating oil leaves the actuator. As a result, although it is possible to prevent the temperature of the operating oil from increasing to a value exceeding a predetermined value, the operating oil with an increased temperature from the oil pump is fed to the actuator, resulting in a reduction of the durability of the actuator.